The dimensions of root systems vary dramatically between plant species, and differ within the same species depending on soil/growth conditions. Roots provide the key mechanism of uptake of water and nutrients for plants by developing a complex network structure within soil. They maintain a symbiotic relationship with microbes by secreting compounds that feed microbes, which then break down organic nutrients into forms that can be more readily absorbed by the roots and utilized by the plant. The robustness of the root system is a key factor to the yield that a plant can produce. It is desirable to have a more dense root system, as increased in root density translates into a faster growth for the plant, which is agriculturally and economically useful.
Further, many biologically active compounds, such as pesticides, are sprayed on the leaves of plants for foliar uptake. Plant leaves are generally waxy with small pores, which make it difficult for the organic molecules to penetrate the leaf. Solutions containing the active compounds typically contain adjuvants that help with the foliar uptake. However, the adjuvants currently used are not very efficient and most of the biologically active compounds do not reach their targets.